This invention relates to a semiconductor memory device which is constructed of MISFETs (insulated gate field-effect transistors).
MIS semiconductor memories hitherto known can be broadly classified into the dynamic memory and the static memory. The static memory is further divided into the type which requires external clocks (clocked static memory) and the type which does not require any external clock (non-clocked static memory).
The dynamic memory and the clocked static memory are of low power dissipation. However, they require external clock signals. Moreover, since the wait time attributed to the clock operation is needed, the cycle time which determines the operating frequency becomes greater than the access time, to bring about the problem that the memories are difficult of use.
On the other hand, with the non-clocked static memory, the cycle time and the access time become equal, and no external clock is necessary. Therefore, the whole system employing this memory is simple, and the memory is easy of use. The non-clocked static memory, however, has the problem that the power dissipation during the operation is high.